The verdict found Ghailani, accused of participating in the 1998 bombings of U.S. embassies in Africa, guilty of conspiracy to damage or destroy U.S. property with explosives, a charge that can carry a penalty of 20 years to life.

"We respect the jury's verdict and are pleased that Ahmed Ghailani now faces a minimum of 20 years in prison and a potential life sentence for his role in the embassy bombings," Matthew Miller, a Department of Justice spokesman, said in a written statement.

"He will face, and we will seek, the maximum sentence of life without parole when he is sentenced in January," added Preet Bharara, the U.S. attorney for the Southern District of New York.

The case, while a narrow win on the merits for federal prosecutors, can be seen as a setback for the Obama administration's goal of trying Guantanamo detainees in civilian courts rather than before military tribunals.

In this case, a 2001 superseding indictment charged Ghailani of conspiring with Osama bin Laden and other members of al Qaeda to kill Americans anywhere in the world, as well as separate charges of murder for the deaths of each of the 224 people killed in the U.S. embassy bombings in Tanzania and Kenya and various other offenses related to the bombings.

While the Department of Justice emphasized that Ghailani will get a lengthy jail sentence, critics are likely to play up the notion that a military court would have been a tidier way of dealing with the case and issues such as torture and treatment detainees may have experienced.

Already, a leading critic of the Obama administration's plan for civilian trials, Rep. Peter King, R-N.Y., the ranking Republican on the House Committee on Homeland Security, said he is "disgusted at the total miscarriage of justice today in Manhattan's federal civilian court."

"This tragic verdict demonstrates the absolute insanity of the Obama administration's decision to try al Qaeda terrorists in civilian courts," King said in a written statement.

In Ghailani's case, a key government witness was not allowed to testify in part because of allegations of torture and how they might have impacted the witness testimony.

"This case was doomed from the beginning when the judge excluded DOJ's key witness who admitted selling the explosives to Ghailani," King said. "Where is the justice for the more than 200 people killed and 4,000 injured in the terrorist bombings of our U.S. embassies in Kenya and Tanzania?"

Nonetheless, a proponent of civilian trials, a professor who has defended a Guantanamo Bay client, remained convinced civilian trials are the correct way to go.

"I agree that it's a setback for the administration, but in a way that reinforces, rather than undermines, the case for civilian court prosecutions," said Stephen I. Vladeck, a law professor at American University Washington College of Law in Washington, D.C. "The risk of acquittal is exactly why civilian trials are more legitimate than military commissions, and today's result bears that out."